Coinbase is a global digital asset exhange company, meaning it is a place to buy and selll crypto currencies. They do have some cryptos that Etoro doesn't have, while Etoro have some cryptos that Coinbase doesn't have, hence it can be good idea to have a profile in both places if you want to start trading cryptos.
One of the advantages of Coinbase is that it also serves as a crypto wallet, where you can store your crypto currencies. Besides that they often offer the possibility to earn crypto while you learn about cryptos, which I think it is a very nice feature on the website. I have done it myself, and I now own some cryptos which I haven't paid for myself. If you are interested in Coinbase, you can follow my guide about how it works here.
First of all you need to make a profile at Coinbase. It takes approximately 5 minutes. Once you are at Coinbase, you click on "Get started". If you access Coinbase through this link, you will get additionally $10 worth of Bitcoin for free, if you make an order for more than $100 dollars. The extra Bitcoin should be in your portfolio within 1 week.
Once you have a profile you are ready to buy some cryptos. The easiest way to get started to buy is by clicking on on "Prices" in the top menu.
Once you have clicked on prices you will acess the various cryptos that you can buy on Coinbase and you can see the different prices. When you have decided which crypto you want to buy, you just click on the blue Trade button to the right.
In my example I chose Bitcoin and I would like to buy €100 worh of Bitcoin and I pay with my creditcard. Meaning you do not need to transfer funds to Coinbase prior to buying cryptos. You just pay with your creditcard.
As an extra security, you will need to preview your order before it goes through. If I buy Bitcoin for €100 I will receive 0.00958736 Bitcoin, as I would also need to pay a fee to Coinbase. Once you click "Buy now", you will be the happy owner of Bitcoin.